Platinum phenanthroline complexes have been found to inhibit Aβ aggregation and reduce Aβ caused neurotoxicity. Our previous results revealed the synergistic roles of phenanthroline ligand and Pt(ii) coordination in the inhibition of Aβ aggregation. In this work, the reactions of PtCl2(phen) with metal bound Aβ complexes were investigated. HPLC results show that the copper coordination decreases the reaction rate of PtCl2(phen) with Aβ1-16 and influences the distribution of products on HPLC profiles. EPR results reveal that Cu(2+) remains coordinated to the Aβ peptide upon the binding of [Pt(phen)](2+), however, the Cu(2+) coordination sites are changed. The formation of bimetallic coordination complex [Pt(phen)+Aβ1-16+Cu(II)] was confirmed by ESI-MS. Tandem MS analysis shows that, similar to the reaction of apo-Aβ peptide, the His6/His14 chelation is also the preferred binding mode for [Pt(phen)](2+) in the presence of copper ions. EPR spectra suggest that the binding of [Pt(phen)](2+) alters the copper coordination from mode I to mode II in Aβ. Tandem MS analysis indicates that His13 and N-terminal amine could be involved in the Cu(2+) coordination in the bimetallic adduct. Similar results were observed in the reaction of Zn(2+) bound Aβ peptide, although the different zinc binding residues were detected in the bimetallic complex. These results indicate that the binding of platinum complex disturbs the most favorable coordination sphere of Cu(2+)/Zn(2+) and turns these metal ions to the secondary coordination site on Aβ. The release of Cu(2+)/Zn(2+) occurs at low pH. This result suggests that the binding of [Pt(phen)](2+) scaffold could interfere with the binding of Zn(2+) and Cu(2+) to Aβ, thus reducing the metal-induced Aβ aggregation and toxicity.

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In spite of their wide application, the cellular uptake of platinum based anticancer drugs is still unclear. The copper transport protein, hCTR1, is proposed to facilitate the cellular uptake of cisplatin, whereas organic cation transport (OCT) is more important for oxaliplatin. It has been reported that both N-terminal and C-terminal metal binding motifs of hCTR1 are highly reactive to cisplatin, which is the initial step of protein assisted cellular uptake of cisplatin. It is still unknown how the platinum drugs in hCTR1 transfer to cytoplasmic media, and whether various platinum complexes possess different activities in this process. Herein, we investigated the reaction of the platinated C-terminal metal binding motif of hCTR1 (C8) with the down-stream protein Atox1. Results show that Atox1 is highly reactive to the platinated C8 adducts of cisplatin and transplatin, whereas the oxaliplatin/C8 adduct is much less reactive. The platinum transfer from C8 to Atox1 occurs in the reaction, which results in the protein unfolding of Atox1. These results demonstrated that the platinated intracellular-domain of hCTR1 is reactive to Atox1, and the reactivity is dependent on the ligand and the coordination structure of platinum complexes. The different reactivity is consistent with the hypothesis that hCTR1 is more significant in the transport of cisplatin than that of oxaliplatin.